Not applicable.
This invention relates to pest control compounds and, more particularly, to compositions effective to control pest molluscs by enhancing the effectiveness of metal poison absorption in molluscs.
Terrestrial pulmonate gastropods such as slugs and snails are significant plant pests that affect commercial agriculture and horticulture and domestic gardens. These organisms are omnivorous and consume large amounts of vegetative material during their daily foraging. Consequently, they can seriously damage vegetable gardens and even plant crops during all phases of the growing cycle. Because of their destructive potential, control measures must be used to ensure adequate protection of the growing plants.
Aquatic molluscs, including the fresh water snails Bulinsu sp., Bulinus, Biomphalaria, and Oncomeania, and vectors of parasitic worms (e.g., Schistosoma), are also pests. Aquatic molluscs are controlled by a number of synthetic and botanical compounds.
Terrestrial pulmonate gastropods and aquatic molluscs are collectively referred to herein as xe2x80x9cmolluscs.xe2x80x9d
A wide variety of approaches have been used to combat pest molluscs. Perhaps the most common is the use of poisonous compounds called molluscicides. Molluscicides encompass a diverse group of chemical compounds including table salt (NaCl), calcium arsenate, copper sulfate and metaldehyde. Molluscicides, depending upon their mode of action, fall into two major groups: (1) contact poisons or (2) ingested poisons. As a contact poison, the molluscicides must come into physical contact with the exterior of the mollusc, either by external application or as a result of the mollusc traversing the bait on the ground. The poison is picked up by the proteinaceous slime coat of the mollusc and builds up in the mollusc""s body until it reaches lethal proportions. One of the major drawbacks of contact-type molluscicides is that they have little effect if the molluscs are not physically touched by the chemical. Slugs or snails will be unaffected if they arc hidden or migrate into an area after application of a contact molluscicide.
One of the few compounds that acts as both a contact and ingested poison is metaldehyde. This compound is commonly used as a long lasting bait, attracting the molluscs and killing them after ingestion of the compound. Despite its high effectiveness and its commercial popularity, metaldehyde is toxic to higher mammals and is a major contributor to domestic animal poisoning in the U.S. and Europe.
Heavy metals, including zinc, aluminum, copper and iron are all toxic to molluscs and are known to be effective molluscicides when used as contact poisons in the form of salts or chelates (Henderson, et al. 1990). Few of them, however, have been successful commercially, perhaps because many such compounds are not palatable to molluscs and are not ingested in sufficient quantities to be effective. More recently, Henderson et al. (UK Patent Application 2 207 866A, 1988) discovered that specific complexes of aluminum with pentanedione compounds and iron with nitroso compounds would act both as ingested and contact poisons.
U.S. Pat. No. 5,437,870 (Puritch et al) discloses an ingestible mollusc poison having a carrier (e.g., a bait), a simple iron compound and a second component. The second component can be ethylene diamine tetracetic acid (EDTA), salts of EDTA, hydroxyethlene triamine diacetic acid, (HEDTA) or salts of HEDTA. Australian Patent Application No. 77420/98 also discloses a stomach-action molluscicide that includes a metal complexone (i.e., iron EDTA) and a carrier.
With the metal-based ingested poisons, the slug must eat and absorb the poison in large enough amounts to reach a lethal threshold. These compounds are much more difficult to formulate and use than are contact poisons, because the compounds are not always palatable to the slug. To be effective, these compounds must be ingested and digested within the mollusc digestive tract in sufficiently high levels to cause a pesticidal effect. However, the activity of Such molluscicides must be slow enough acting to prevent the slug from prematurely becoming sick and to cease feeding on the poison before a lethal dose is ingested. (Henderson and Parker, 1986.) Many of the contact poisons (e.g., aluminum sulfate, copper sulfate, borax, etc.) are useless as ingested poisons because of their deterrence to slugs.
It would thus be desirable to provide a composition that will enhance absorption of stomach-action mollusc poisons without deterring ingestion of the poison by molluscs.
The invention provides a mollusc stomach poison composition that comprises a simple metal compound, an additive that enhances the activity and absorption of the metal, and a carrier material that is edible to molluscs. The composition is effective to kill molluscs upon being ingested by the mollusc.
The simple metal compound may include metals selected from the group consisting of iron, copper, zinc, aluminum, and mixtures thereof. The term xe2x80x9cironxe2x80x9d as used herein is understood to refer to both the ferric and ferrous forms of iron. The activity enhancing additive is a compound selected from the group consisting of ethylene diamine disuccinic acid, isomers of ethylene diamine disuccinic acid, salts of ethylene diamine disuccinic acid, metal complexes of ethylene diamine disuccinic acid and mixtures thereof. The carrier material is one that is edible to molluscs, and it preferably is a mollusc food.
In another embodiment the composition comprises a metal complex of ethylene diamine disuccinic acid or isomers thereof. Metals from which the complex can be formed include iron, copper, zinc, and aluminum.
In another embodiment the mollusc poison composition may also include a co-active ingredient, such as metaldehyde. In yet another embodiment the composition may include or be used with a fertilizer compound, such as a granular fertilizer.
As used herein, the term xe2x80x9cmolluscxe2x80x9d refers to both terrestrial and aquatic molluscs.
The present invention provides a composition that is an ingestible mollusc poison. In one embodiment, the composition includes a simple metal compound, an activity-enhancing additive which is believed to increase the efficacy of the metal compound, and a carrier that is edible to molluscs. Additional formulation enhancing additives may be included as well. Examples of such compounds include pH-adjusting compounds, preservatives, anti-microbial agents, phagostimulants, and taste-altering additives.
The simple metal compound can be one that includes metals such as iron, copper, zinc, aluminum or mixtures thereof. Such a compound may be reduced elemental iron, metal proteins (e.g., iron proteins, copper proteins, zinc proteins, aluminum proteins), metal salts (e.g., iron salts, copper salts, zinc salts, aluminum salts and mixtures thereof), metal carbohydrates (e.g., iron carbohydrates, copper carbohydrates, zinc carbohydrates, aluminum carbohydrates and mixtures thereof). Specific examples of such compounds include iron acetate, iron chloride, iron phosphate, iron phosphate/sodium citrate mixture, sodium iron phosphate, iron pyrophosphate, iron nitrate, iron ammonium sulfate, iron albuminate, iron sulfate, iron sulfide, iron choline citrate, iron glycerol phosphate, iron citrate, iron ammonium citrate, iron fumarate, iron gluconate, iron lactate, iron saccharate, iron fructate, iron dextrate, iron succinate, iron tartrate, copper acetate, copper chloride, copper phosphate, copper pyrophosphate, copper nitrate, copper ammonium sulfate, copper albuminate, copper sulfate, copper gluconate, copper lactate, copper saccharate, copper fructate, copper dextrate, zinc acetate, zinc chloride, zinc phosphate, zinc pyrophosphate, zinc nitrate, zinc ammonium sulfate, zinc albuminate, zinc sulfate, zinc gluconate, zinc lactate, zinc saccharate, zinc fructate, zinc dextrate, aluminum acetate, aluminum chloride, aluminum phosphate, aluminum pyrophosphate, aluminum nitrate, aluminum ammonium sulfate, aluminum albuminate, aluminum sulfate, aluminum gluconate, aluminum lactate, aluminum saccharate, aluminum fructate, and aluminum dextrate. It is understood that the term xe2x80x9cironxe2x80x9d as used herein refers to both the ferric and ferrous forms of this element.
As noted above, the activity enhancing additive is one that improves the efficacy of the metal compound by enhancing the digestive absorption of the metal. A preferred activity enhancing additive is ethylene diamine disuccinic acid (EDDS), in both its naturally occurring and synthetic forms. Further, the activity enhancing additive may be in the form of isomers of ethylene diamine disuccinic acid, salts of ethylene diamine disuccinic acid, metal complexes of ethylene diamine disuccinic acid and mixtures thereof.
Activity enhancing additives such as EDDS, its isomers, and its derivatives, are believed to contribute to the rapid absorption of the simple metal compound from the mollusc digestive tract into the internal organs of the animal. This results in rapid, irreversible destruction of the cellular integrity of the mollusc which prevents continuing feeding on plant material, eventually leading to death. EDDS is believed to affect parts of the mollusc digestive system by allowing the metal to be more freely and quickly dispersed throughout the mollusc body. The result of such overload of metal results in pathological distress to the mollusc system.
EDDS is a hexadentate ligand that occurs naturally and which is produced by a number of microorganisms including the actinomycete, Amycolatopsis japonicum sp. nov. (Nishikori et al. J. Antibiot. 37:426-427 (1994); Goodfellow et al, Systematics and Applied Microbiology 20.78-84 (1997). The molecular formula for this compound is C10H16N2O2 for the acid and C10H13N2O8Na3 for the trisodium salt. The acid has a molecular mass of 292.25 while the trisodium salt is 358.19. The compound can occur in three stereoisomers, [R,R], [R,S/S,R], and [S,S]. EDDS can also be synthesized by a reaction of L-aspartic acid and 1,2-dihaloethane, as disclosed in U.S. Pat. No. 5,554,791.
EDDS has been developed commercially as a trisodium salt compound sold under the trademark Octaquest(copyright) E-30 by the Associated Octel Company Ltd. This compound has the ability to complex with metals to serve as a chelator. It has the advantage of easily biodegrading and does not persist in the environment (Schowanek et al., Chemosphere 34:2375-2391 (1997)). Hence, it has been proposed for use as a surfactant in laundry detergents as disclosed in U.S. Pat. No. 4,704,233.
Useful salts of ethylene diamine disuccinic acid that may serve as an activity enhancing additive according to the present invention include alkali metal salts, alkali earth salts, ammonium salts and substituted ammonium salts of this compound, as well as mixtures thereof. Preferred salts include the sodium, potassium, and ammonium salts.
The activity enhancing additive may also be in the form of metal complexes of ethylene diamine disuccinic acid. Examples of such complexes include iron EDDS complexes, as well as copper, zinc, and aluminum complexes of EDDS. In one embodiment, the composition may be used without a simple metal compound as a separate component. Instead, the compound can be used in the form of a metal complex of EDDS, with metals selected from iron, copper, zinc, and aluminum.
Suitable carrier materials are those that are edible to molluscs. Mollusc foods are an example of a preferred type of carrier material. Examples of suitable mollusc food carriers include wheat flour, wheat cereal, agar, gelatin, oil cake, pet food wheat, soya, oats, corn, citrus mash, rice, fruits, fish by-products, sugars, coated vegetable seeds, coated cereal seeds, casein, blood meal, bone meal, yeast, fats, beer products, and mixtures thereof. Examples of particularly useful mollusc foods include a bone mealxe2x80x94wheat flour mixture having a ratio of bone meal to wheat flour in the range of 50:50 to 90:10 and one formed from wheat flour and sugar at a ratio of wheat flour to sugar in the range of about 90:10 to 95:5.
Other compounds, as noted above, may be added to the composition as formulation enhancing additives. Such compounds include preservatives or anti-microbial agents, phagostimulants, waterproofing agents, taste altering additives, and pH-adjusting additives.
Exemplary preservatives include Legend MK(copyright), available from Rohm and Hass Company of Philadelphia, Pa. and CA-24, available from Dr. Lehmann and Co. of Memmingen/Allgxc3xa4u, Germany. Preservatives such as these can normally be mixed with water to form a stock solution to be added to the formulation at a concentration in the range of about 10-750 ppm.
Phagostimulants can be added to the composition to attract molluscs and to induce molluscs to feed upon the composition. A variety of phagostimulants can be used, including sugars, yeast products, and casein. Sugars, such as sucrose, are among the more preferred phagostimulants. These additives are normally incorporated within the composition in a dry form. Typically, they can be added to the composition at about I to 2.5% by weight of the total composition.
Waterproofing agents, which can also act as binders, can be added to the composition to improve the weatherability of the composition. These are typically water insoluble compounds such as waxy materials and other hydrocarbons. Examples of suitable waterproofing agents are paraffin wax, stearate salts, beeswax, and similar compounds. One preferred wax compound is PAROWAX(copyright), available from Conros Corp. of Scarborough, Ontario, Canada. Waterproofing agents can be incorporated into the composition in dry form, at about 5 to 12% by weight of the total composition.
It is also desirable to include within the composition taste altering compounds that render the composition unpalatable to animals, such as humans and pets. Exemplary compositions include those having a bitter taste. One such compound is commercially available as BITREX(copyright) from McFarlane Smith Ltd. of Edinburgh, Scotland. These compounds typically are added at a very low concentration. For example, a 0.1% BITREX solution can be added to the composition at about 1 to 2% by weight of the total composition.
Useful pH-affecting additives include calcium carbonate, potassium carbonate, potassium hydroxide, ascorbic acid, tartaric acid, and citric acid. Such additives may be used at a concentration in the range of about 0.2 to 5.0% by wt., and they should be effective to adjust the pH to within a range of about 5 to 9.
The molar ratio of the metal in the simple metal compound to the activity enhancing additive may be in the range of about 1:0.02 to 1:58. More preferably, this ratio is in the range of 1:0.3 to 1:12. Further, the metal in the simple metal compound may be present at a concentration range of about 200 to 20,000 ppm (0.02 to 2.0% by weight) while the activity enhancing additive may be present at a concentration in the range of about 2,000 to 60,000 ppm (0.2 to 6.0% by weight of the composition). One exemplary concentration range is about 0.1 to 0.5% by wt. of the composition for the metal and about 0.8 to 6.0% by wt. for the EDDS component.
Where the composition is used without a simple metal compound, i.e., in the form of a metal complex of EDDS, the metal complex can be present at 5000 to 90,000 ppm (0.5 to 9.0% by wt.).
In one embodiment the composition may also include a co-active molluscicidal agent. One such co-active molluscicidal agent is metaldehyde. Other potential co-active molluscicidal agents include methiocarb, carbaryl, isolan, mexcarbate, niclosamide, trifenmorph, carbofuran, anarcardic acid, and plant-derived saponins. Such co-active ingredients may be added to the composition at a concentration in the range of about 0.2 to 5.0% by wt.
In yet another embodiment the composition may also include a fertilizer, such as virtually any plant fertilizer. Suitable fertilizers typically are granular and an example of one useful fertilizer is Ironite(copyright), available from Ironite Products Company of Scottsdale, Ariz. When present, fertilizers may be used at a concentration in the range of about 0.5 to 10.0% by weight of the composition.
The composition of the invention typically is used in dry form and many of the constituent ingredients of the composition are included in dry form. However, it is often useful to include a sufficient amount of water within the composition to form a dough so that the ingredients can be more easily blended. Water is typically added at a concentration of about 15 to 60% by weight of the total composition. Water, however, typically is driven off by heating and drying the molluscicidal bait before it is used. The composition may also be formulated as a liquid, especially where the composition utilizes a metal complex of EDDS.
As noted above, the composition of the present invention is typically used in a dry, spreadable form such as powders, granules, cubes, or pellets. The composition may be spread on or around areas infested by molluscs as well as in areas in which mollusc infestation is to be prevented. When used to combat aquatic molluscs the composition can simply be added to the environment inhabited by the molluscs.
To prepare the composition, a suitable amount of the simple metal compound and the activity enhancing additive can be blended in dry form, with a dry carrier material. Thereafter, other dry ingredients (such as phagostimulants and waterproofing agents) are blended and mixed with the bait. Next, suitable amounts of liquid additives (such as preservatives, taste altering additives and water) are added to the dry mixture to form a dough. The bait can be covered, such as with a plastic wrap, and heated. One preferred heating technique is by heating in a microwave oven for 30 seconds to 10 minutes. After heating, the dough can be processed in a food grinder to obtain strands of the molluscicidal composition. This material is then dried, at elevated or ambient temperatures, and it can be made into a desired form, such as powder, pellets or granules.
One exemplary molluscicidal composition can be prepared as follows. First, metal compounds, e.g. iron carbohydrate or iron salts, are dry blended into a cereal flour (wheat) at between 1000 to 20,000 ppm metal wt/wt. Dry EDDS, or its sodium salt, is then added to the flour on a molar level to the amount of iron added. This level can vary in the range of a metal: EDDS molar ratio in the range of about 1:0.02 to 1:58 ratio. The EDDS is added to the mixture while continually stirring. Other ingredients can be added to the mixture, such as, anti-microbials (Legend(copyright)), waterproofing agents, and phagostimulants (e.g., sugar). Water soluble additives are dissolved in water and then the water is blended into the dry wheat/iron compounds plus EDDS mixture. The dough is thoroughly mixed in a grinding device and extruded in the form of noodles. The resultant bait is dried at 40 degrees Celsius for 24 hours before testing.
The metal complexes can be synthesized by combining virtually any soluble metal compound, such as ferrous sulfate, with soluble EDDS or virtually any soluble derivative of EDDS. Following this combination, the pH can be adjusted (e.g., in the range of about 5 to 9) with a suitable agent such as a concentrated solution of potassium hydroxide. Exemplary metal compounds include reduced elemental iron, metal proteins (e.g., iron proteins, copper proteins, zinc proteins, aluminum proteins), metal salts (e.g., iron salts, copper salts, zinc salts, aluminum salts and mixtures thereof), metal carbohydrates (e.g., iron carbohydrates, copper carbohydrates, zinc carbohydrates, aluminum carbohydrates and mixtures thereof). Specific examples of such compounds include iron acetate, iron chloride, iron phosphate, iron phosphate/sodium citrate mixture, sodium iron phosphate, iron pyrophosphate, iron nitrate, iron ammonium sulfate, iron sulfide, iron albuminate, iron choline citrate, iron glycerol phosphate, iron citrate, iron ammonium citrate, iron fumarate, iron gluconate, iron lactate, iron saccharate, iron fructate, iron dextrate, iron succinate, iron tartrate, copper acetate, copper chloride, copper phosphate, copper pyrophosphate, copper nitrate, copper ammonium sulfate, copper albuminate, copper sulfate, copper gluconate, copper lactate, copper saccharate, copper fructate, copper dextrate, zinc acetate, zinc chloride, zinc phosphate, zinc pyrophosphate, zinc nitrate, zinc ammonium sulfate, zinc albuminate, zinc sulfate, zinc gluconate, zinc lactate, zinc saccharate, zinc fructate, zinc dextrate, aluminum acetate, aluminum chloride, aluminum phosphate, aluminum pyrophosphate, aluminum nitrate, aluminum ammonium sulfate, aluminum albuminate, aluminum sulfate, aluminum gluconate, aluminum lactate, aluminum saccharate, aluminum fructate, and aluminum dextrate. Exemplary derivatives of EDDS include isomers of ethylene diamine disuccinic acid, salts of ethylene diamine disuccinic acid, including alkali earth, alkali metal, ammonium, substituted ammonium, mixtures of these salts, metal complexes of ethylene diamine disuccinic acid and mixtures thereof.